The oldest venomous vertebrate yet found was a small-dog-sized early relative of mammals named Euchambersia that lived some 260 million years ago, according to findings just published in the journal PLOS One by scientists from University of the Witwatersrand (WITS).

"Today, snakes are notorious for their venomous bite," said the study's lead author Julien Benoit in a statement, "but their fossil record vanishes in the depth of geological times at about 167 million years ago. So, at 260 million years ago, the Euchambersia evolved venom – more than a 100 million years before the very first snake was even born."

Euchambersia was about 16-20 inches long (40-50 centimeters) and trod the land of modern-day South Africa well before the dinosaurs. The animal has long been supposed to have been venomous, based on characteristics of its teeth and upper jaw, but the hypothesis had not until now been tested.

The WITS researchers used CT scanning and 3D imaging on the only two fossilized skulls in existence of Euchambersia. Sure enough, under the detailed examination they found the small creature's anatomy had characteristics consonant with making venom.

The scientists found a deep, wide space in the upper jaw called a fossa that would have held a venom gland. It was connected to the canine teeth and mouth by bony grooves and canals. Finally, ridges on the incisors and canine teeth completed the venom delivery system.

Euchambersia did not deliver its venom in the same way snakes deliver their payload, the scientists found. While reptiles such as the cobras and vipers we all know and run from today inject venom through needle-like grooves in the their teeth, Euchambersia's venom went directly into its mouth and the animal used the ridges on its canines to pass the poison to its victims.

An early paleontologist named Franz Nopcsa would likely be gladdened by the findings, were he alive today. Nopcsa in 1933 studied an Euchambersia fossil and averred that the creature was likely the oldest venomous animal anyone had ever documented. But venom glands don't fossilize, and fancy CAT scans and 3D imaging systems did not exist in his day, so he could never know for sure if he was right.

"The results? Nopcsa was right," Benoit wrote in The Conversation, naming Euchambersia "officially the oldest venomous animal that ever roamed the Earth."

"Even more intriguing is that Euchambersia is related to early mammals, not to snakes," Benoit noted in the piece, adding that some scientists think all mammals were once venomous but over time lost their venom-producing glands, leaving a comparative few modern mammals – vampire bats, some shrews, for example – with poisonous ways.